Comet Holmes now bigger than our Sun

[rhoenix]

Formerly, the Sun was the largest object in the Solar System. Now, comet 17P/Holmes holds that distinction.

Spectacular outbursting comet 17P/Holmes exploded in size and brightness on October 24. It continues to expand and is now the largest single object in the Solar system, being bigger than the Sun (see Figure). The diameter of the tenuous dust atmosphere of the comet was measured at 1.4 million kilometers (0.9 million miles) on 2007 November 9 by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. They used observations from a wide-field camera on the Canada-France-Hawaii Telescope (CFHT), one of the few professional instruments still capable of capturing the whole comet in one image. Other astronomers involved in the UH program to study the comet include Bin Yang, Nuno Peixinho and David Jewitt. The present eruption of comet Holmes was first reported on October 24 and has continued at a steady 0.5 km/sec (1100 mph) ever since. The comet is an unprecedented half a million times brighter than before the eruption began. This amazing eruption of the comet is produced by dust ejected from a tiny solid nucleus made of ice and rock, only 3.6 km (roughly 2.2 miles) in diameter.

Caption: (Left) Image of comet Holmes from the 3.6-meter Canada-France-Hawaii telescope on Mauna Kea showing the 1.4 million km diameter coma. The white ''star'' near the center of the coma is in fact the dust-shrouded nucleus. (Right) the Sun and planet Saturn shown at the same scale for comparison. (Sun and Saturn images courtesy of NASA's SOHO and Voyager projects). [The same image is available here as a 300 dpi tif file.]

The new image also shows the growth of a tail on comet Holmes (the fuzzy region to the lower right in the comet picture), caused by the pressure of sunlight acting on dust grains in the coma. Over the next few weeks and months, the coma and tail are expected to expand even more while the comet will fade as the dust disperses. Comet Holmes showed a double outburst in November 1892 and January 1893. It is not known if the present activity in the comet will follow the pattern from 1892, but continued observations from Mauna Kea are planned to watch for a second outburst. Most comets show small fluctuations in brightness and some have distinct outbursts. The huge event on-going in comet Holmes is unprecedented, however.

The orbit period of comet Holmes is about 6 years, putting it in the class of Jupiter Family Comets whose orbits are strongly influenced by Jupiter. These objects are thought to have spent most of the last 4.5 billion years orbiting the Sun beyond Neptune, in a region known as the Kuiper Belt. Holmes probably was deflected into its present orbit within the last few thousand years and is losing mass as it evaporates in the heat of the Sun. In another few thousand years it is likely either to hit the Sun or a planet, be ejected from the Solar system, or simply die by running out of gas.

While the name of this comet makes me chuckle, especially given it's size now, this is fascinating stuff.

[Alan Bolte]

Size, to me, suggests volume. Now, if you want to say it's longer than the sun is wide, that seems a far more reasonable statement.

[Androsphinx]

Size, to me, suggests volume. Now, if you want to say it's longer than the sun is wide, that seems a far more reasonable statement.

The volume -is- larger. It's a vaguely spherical corona with a diameter of 1.4 million km, just a touch bigger than that of the sun, but expanding. Did you even look at the picture?

[Big Phil]

Size, to me, suggests volume. Now, if you want to say it's longer than the sun is wide, that seems a far more reasonable statement.

The volume -is- larger. It's a vaguely spherical corona with a diameter of 1.4 million km, just a touch bigger than that of the sun, but expanding. Did you even look at the picture?

The article says "bigger than the sun," which is highly misleading. Its volume is greater than the sun, but its mass is nowhere near that of the sun. Sounds clever, but not nearly as impressive when you read the details.

[Dooey Jo]

That's nice of them to use the "corona" of the comet, but not include the Sun's corona, which extends several million kilometres above the surface of the Sun itself (or hey, why not include the solar wind too, that only covers roughly the whole solar system). Though I suppose one can say whatever misleading things one wants in the interests of popular science...

[Androsphinx]

I think it's more that the corona is not generally considered part of the sun for measuring, etc; whereas the dust around a comet (which I called the "corona", I don't think that the article did) is. So it's a definitional thing.

Still, very cool nevertheless

[Winston Blake]

The article says "bigger than the sun," which is highly misleading. Its volume is greater than the sun, but its mass is nowhere near that of the sun. Sounds clever, but not nearly as impressive when you read the details.

So you think it's 'highly misleading' for me to say that beach balls are bigger than bowling balls?

[Dooey Jo]

I think it's more that the corona is not generally considered part of the sun for measuring, etc; whereas the dust around a comet (which I called the "corona", I don't think that the article did) is. So it's a definitional thing.

Normally when a comet's size is mentioned, it is in the range of tens of kilometres, and so obviously means the nucleus, not the coma or the tail (unless they say it is "50 million kilometres long"). It's not even gravitationally bound, FFS...

[Alan Bolte]

My bad, didn't even think to check if there would be pics.

[Big Phil]

The article says "bigger than the sun," which is highly misleading. Its volume is greater than the sun, but its mass is nowhere near that of the sun. Sounds clever, but not nearly as impressive when you read the details.

So you think it's 'highly misleading' for me to say that beach balls are bigger than bowling balls?

Try another analogy - yours is terrible

[CmdrWilkens]

The article says "bigger than the sun," which is highly misleading. Its volume is greater than the sun, but its mass is nowhere near that of the sun. Sounds clever, but not nearly as impressive when you read the details.

So you think it's 'highly misleading' for me to say that beach balls are bigger than bowling balls?

Try another analogy - yours is terrible

Not really, all objects are spherical with mass and in the analogy the beach ball is large with low mass while the bowling ball is smaller with greater mass given the subject at hand its hardly a poor analogy.

[Big Phil]

So you think it's 'highly misleading' for me to say that beach balls are bigger than bowling balls?

Try another analogy - yours is terrible

Not really, all objects are spherical with mass and in the analogy the beach ball is large with low mass while the bowling ball is smaller with greater mass given the subject at hand its hardly a poor analogy.

You're not seriously defending Blake's red herring, are you?

[rhoenix]

You're not seriously defending Blake's red herring, are you?

Please explain as to how his analogy was a red herring. As far as I read, it fit the scenario perfectly, because as you stated, mass is different from volume; additionally "bigger" nearly always in common parlance denotes volume, not mass.

The analogy showed that while the comet is physically larger (in volume) than our sun, it was less massive.

[Soontir C'boath]

You're not seriously defending Blake's red herring, are you?

Although a beach ball doesn't have a core like a bowling ball and the celestial objects, it's still an apt analogy given what you wrote.

[Androsphinx]

Please explain as to how his analogy was a red herring.

Because he said that it was?

[rhoenix]

Please explain as to how his analogy was a red herring.

Because he said that it was?

I said "explain," not "restate."

[wolveraptor]

Blake's analogy is just fine, but I agree with Sanchez that the article is misleading. When speaking in astronomical terms, it's dumb not to specify whether one is referring to volume or mass. You'll never hear real astronomers being that unspecific.

[rhoenix]

Blake's analogy is just fine, but I agree with Sanchez that the article is misleading. When speaking in astronomical terms, it's dumb not to specify whether one is referring to volume or mass. You'll never hear real astronomers being that unspecific.

That I'll concede - the site itself didn't appear very formal, and therefore seemed more "lol hay look guys!" than scientifically informative.

[Big Phil]

You're not seriously defending Blake's red herring, are you?

Please explain as to how his analogy was a red herring. As far as I read, it fit the scenario perfectly, because as you stated, mass is different from volume; additionally "bigger" nearly always in common parlance denotes volume, not mass.

The analogy showed that while the comet is physically larger (in volume) than our sun, it was less massive.

It's a red herring because I said nothing about beach balls or bowling balls, nor did I say it was technically incorrect; I simply said it was misleading.

[Big Phil]

to elaborate, bigger implies larger and more massive; I know that's not technically true, but the sensational title certainly doesn't clarify

[rhoenix]

Another source, with less "lol look at this:"

The Sun is no longer the largest object in our solar system. The recently visible-to-the-naked-eye Holmes comet has achieved that distinction today. The comet has a larger gas and dust cloud known as the coma, and consequently it has a larger diameter than the sun according to astronomers at the University of Hawaii. Scientists don't seem to have a guess as to how big it will ultimately become.

The Holmes coma's diameter on Nov. 9 was 869,900 miles (1.4 million kilometers), based on measurements by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. The sun's diameter, stated differently by various sources, is about 864,900 miles (1.392 million kilometers).Holmes is still visible to the naked eye as a fuzzy star anytime after dark, high in the northeast sky. You can find it by using this sky map.

On Monday, Nov. 19, the comet will create a unique sky watching event according to the Web site Spaceweather.com: "The comet will glide by the star Mirfak [also called Alpha Persei] and appear to swallow it-a sight not to be missed.

"NASA's Hubble Space Telescope has watched the bright core of Comet 17P/Holmes, which mysteriously brightened by nearly a millionfold in a 24-hour period beginning Oct. 23, 2007. "This amazing eruption of the comet is produced by dust ejected from a tiny solid nucleus made of ice and rock, only 3.6 kilometers (roughly 2.2 miles) in diameter," The Hawaiian astronomy team wrote in a press statement. The new image from the Hawaiian observatory also shows a modest tail forming to one side, now just a fuzzy region to the lower-right. That's caused by the pressure of sunlight pushing on the gas and dust of the coma. But the comet is so far away-149 million miles (240 million kilometers), or about 1.6 times the distance from Earth to the sun-that even Hubble can't resolve its nucleus.

Comets have gotten a lot of attention this year. For example, in October NASA said one of its satellites captured the image of a solar hurricane ripping off the tail of a passing comet. The resulting collision saw the complete detachment of the plasma tail of Encke's comet, which was traveling within the orbit of Mercury, NASA said. The comet is only the second repeating, or periodic, comet ever identified and has the shortest orbital period - about 3.3 years - of any known comet. Halley's comet was the first.

That's a bit less ambiguous than the earlier article.

[wolveraptor]

It's a red herring because I said nothing about beach balls or bowling balls

You're a fucking idiot. Do you understand the purpose behind an analogy? The fucking point is that you use two completely different nouns to give an example of a similar circumstance. Of course you said nothing about beach or bowling balls...Christ...

nor did I say it was technically incorrect; I simply said it was misleading.

And so Blake brought up the point that it would not be misleading to call a beach ball bigger than a bowling ball, at which point you should've responded by saying that it is misleading in the context of astronomy. Instead, you chose the retard route and spouted some shit about red-herrings, demonstrating your inability to grasp the concept of analogy.

[Winston Blake]

to elaborate, bigger implies larger and more massive; I know that's not technically true, but the sensational title certainly doesn't clarify

Ok, consider how here you're using the word 'larger' to mean 'purely more volume'. If the title had instead been Comet Holmes now larger than our Sun, then I fully expect that you would have come out and said it was being misleading as well.

I think it makes sense just fine for the title to use either 'bigger' or 'larger'. I have to assume that your dialect is slightly different from what I think is normal.

I don't see why it needs clarifying. See below.

Blake's analogy is just fine, but I agree with Sanchez that the article is misleading. When speaking in astronomical terms, it's dumb not to specify whether one is referring to volume or mass. You'll never hear real astronomers being that unspecific.

Fair enough, but you don't need to be an astronomer to realise that a solar mass object floating around our solar system could never be classified as a comet.

[Big Phil]

Much as I hate to admit it, Wolveraptor is right. I should have just address Winston Blake's post.

My response would have been something like - yes, saying a beach ball is bigger than a bowling ball would be misleading... because to me bigger implies both volume and mass. Saying its diameter or volume is greater than that of the sun is fine, saying it's more massive would be flat out wrong, but saying it's bigger, while not technically incorrect, leads to misunderstandings and false conclusions.

[Winston Blake]

My response would have been something like - yes, saying a beach ball is bigger than a bowling ball would be misleading... because to me bigger implies both volume and mass. Saying its diameter or volume is greater than that of the sun is fine, saying it's more massive would be flat out wrong, but saying it's bigger, while not technically incorrect, leads to misunderstandings and false conclusions.

Ok, problem solved. Our dialects must be slightly different.